A polyoxyethylene sorbitan fatty acid ester obtained by adding ethylene oxide to a sorbitan fatty acid ester which is a partial ester of sorbitol or sorbitan and a fatty acid is known to be excellent in properties such as emulsifying ability, dispersing ability, and wetting ability and has been employed in a wide variety of uses such as cosmetics, lubricants, synthetic resins, and detergents.
Moreover, among the polyoxyethylene sorbitan fatty acid esters, polysorbate 80 is a substance described in Japanese Pharmacopoeia and polysorbates 20, 40, 60, and 65 are substances described in Japanese Pharmaceutical Excipients and they are generally widely used as pharmaceutical additives. Furthermore, in Europe and America, these polysorbates have actual performance of being permitted and have employed as food additives and, also in Japan, are in the course of preparation for permission at an early date as food additives. Thus, the polyoxyethylene sorbitan fatty acid esters have used in a wide range of fields.
However, as physical properties of the polyoxyethylene sorbitan fatty acid esters, they are substances which generally give feeling of bitter taste, oxidation odor, and deterioration odor, for example, as described that “the taste is slightly bitter and slight characteristic odor is present” as properties of polysorbates 40, 60, and 65 in Japanese Pharmaceutical Excipients and polysorbate 80 in Japanese Pharmacopoeia. Therefore, they are avoided in some cases in the fields such as foods and oral cosmetics where their taste is greatly regarded as important.
As production processes for improving the bitterness of the polyoxyethylene sorbitan fatty acid esters, there have been reported a process of performing a steam treatment or a distillation treatment (Patent Document 1) and a process of performing a dehydration-adsorption treatment with a specific adsorbent in the presence of water (Patent Document 2).    Patent Document 1: JP-A-2005-23227    Patent Document 2: JP-A-2007-91852